A valve assembly employed with a high-pressure pump is continuously subjected to changing pressure loads, which vary as a function of the number of strokes of an associated plunger. As the suction pressure of the pump generally equals the atmospheric pressure, load changes in the ratio of 2,000 to 1 or more are encountered. The components of the valve assembly can withstand such load changes only for a limited extent of time, i.e. the material from which the valve components are formed often fails after a short period of service. Replacement of the valve components of the valve assembly is very time-consuming and the operating period of the high-pressure pumps is relatively short.